The present invention is directed generally to centrifugal fluid separation devices and more particularly involves a pressure driven and/or balanced separation device preferably having a simplified disposable tubing and bag set used with a loopless, rotating sealless rotor.
A number of fluid separation devices have been known and various models are currently available for the separation of blood or other composite fluids into the various component elements thereof. For example, a variety of centrifugal machines are available for separating blood into component elements such as red blood cells, platelets and plasma, inter alia.
Centrifugation for such purposes has come in many forms in both continuous and batch types. For example, in the widely used process known as continuous centrifugation, as generally opposed to batch process centrifugation, a continuous input of a composite fluid is flowed into the separation device or chamber while at the same time the components of that composite fluid are substantially continuously separated and these separated components are usually then also substantially continuously removed therefrom. Many currently popular forms of such continuous fluid separation devices include loops of entry and exit flow tubing lines connected to the separation centrifuge chamber such that each loop is rotated in a relative one-omegaxe2x80x94two-omega (1xcfx89xe2x88x922xcfx89) relationship to the centrifuge chamber itself so that the tubing lines will remain free from twisting about themselves.
An alternative form of tubing line connection to a continuous centrifugal separation device is also available in the art which does not have such a loop, but which instead requires one or more rotating seals at the respective connections of the tubing lines to the centrifuge separation chamber, again to maintain the tubing lines free from twisting.
Batch-type centrifugation, on the other hand, usually involves separation of a composite fluid such as whole blood in a closed container, often a deformable bag, followed by a usually complicated process of automated and/or manual expression of one or more of the separated components out of the separation container or bag. A great deal of control, either automated, such as by optical interface detection, or by a diligent human operator watching a moving interface, is required with such previous batch-type processes. Indeed, various means and methods have been used in prior centrifugal separation devices, both continuous and batch, for driving fluid flow and maintaining desirable interface position control between the component elements being separated thereby. For example, as mentioned, various optical feedback methods and devices have been employed in the art. Various pumping and valving arrangements are also used in various of these and other arrangements. Alternative relatively automatic volume flow and density relationship interface controls have also been used; for example, in a continuous system by the disposition of control outlet ports in strategic locations relative to the separated component outlet ports.
Nevertheless, many facets of these prior separation devices, though satisfactorily productive, may provide certain features which are less efficient than a desired optimum. For example, centrifugal separation devices using loops of tubing lines rotated in the above-described 1xcfx89xe2x88x922xcfx89 relationship with the centrifuge separation chamber require significant, usually substantially large drive mechanisms which thereby mandate that each such entire device then also be necessarily of a relatively large scale. Rotating seal devices, on the other hand, require intricate and often operationally problematic rotating seal structures. Still further, prior fluid drive and/or interface control systems have generally been either overly complex, as in the case of most of the optical control models, and/or automatic volume flow/density controls may not be entirely efficient in separation due to the usually inherent re-mixing of some quantities of the centrifugally separated components.
Hence, substantial desiderata remain to provide more highly efficient centrifugal separation devices in terms of increased efficiency fluid flow drive and separation interface controls; reduced rotor drive mechanization, quantity and/or scale; and/or reduced seal need and/or intricacy. It is toward any one or more of these or other goals as may be apparent throughout this specification that the present invention is directed.
The present invention is directed generally to centrifugal fluid separation devices and/or systems for use in centrifugally separating composite fluids into the component elements thereof. Such centrifugal separation systems include unique centrifugal rotor and rotor/fluid container combinations in which each rotor, preferably with a plurality of containers positioned therein, may together be disposed in a freely rotatable disposition relative to the rotational drive unit. Freely rotatable indicates loopless and rotating sealless as well as the preference that the rotors may be magnetically or otherwise non-invasively driven. A totally closed system may thus also be preferably provided hereby with simple sterilization and disposability of the fluid container/tubing combination and/or the rotor.
Each rotor has a substantially central composite fluid receiving/containing area, at least one component collection area and at least one fluid flow channel defined therein. In a preferred embodiment, a composite fluid to be separated into component parts may then be delivered to the fluid receiving or containment area preferably in a composite fluid container or bag. Then, under centrifuge conditions, the composite fluid may travel from the composite fluid container through a radial fluid inlet channel to a circumferential fluid separation channel where under subjection to centrifugal forces, the composite fluid may be separated into respective components. These components may then travel through respective circumferential channel portions to respective component collection areas where they are preferably collected in collection containers or bags. These separated fluids may then be removed from the separation device in or from the collection bag or bags for storage, further processing or may then be returned to the donor. The composite fluid is preferably whole blood, and the respective components may then be plasma and red blood cells (RBCs), although buffy coats and/or platelets, inter alia, may also be harvested herewith.
The respective circumferential channel portions preferably include and/or are connected with first and second fluid outlet channel portions through which the separated components may flow to the respective collection areas. These first and second outlet channels preferably have respective first and second outlets which are preferably located at relative radial positions that are selected to be related to each other so as to provide a substantial hydraulic or hydrostatic fluid pressure balance between the outlets for the respective separated fluids flowing therethrough. Such a fluid pressure balance preferably controls the desired location of the interface between the separated fluid components within the circumferential separation channel. The preferred outlet channel height relationship which provides this hydraulic balance may be derived from the general hydrostatic equation xcfx812g2h2=xcfx813g3h3 wherein the height or radial distance of the firs outlet channel is h2, and the height or radial distance of the second outlet channel is h3. These relative lengths, h2 and h3, may then be selected so as to provide the appropriate preferred pressure balance given a separable composite fluid to be flowed in separated fluid component parts therethrough. The other variables in the above equation are either fluid dependent, see e.g., xcfx812 and xcfx813 which represent the respective densities of the separated fluids in the first and second outlet channels, or are otherwise relatively non-selectable and/or for the most part not as consequential or are relatively non-governing in the general equation; e.g., the g2 and g3 variables are gravitational acceleration values representing the respective average g value in each of the two columns, which maybe a similar, if not a substantially equal value (i.e., even though there is likely a distinction, g2 may generally vary a relatively small amount from g3) in normal operation. Hence, however, the dominant driving, selectable differences will be in the relative heights h2 and h3 which may simply be chosen to accommodate for any differences in the other terms, xcfx81 or g.
Thus, for a composite fluid such as whole blood, where the respective densities of the separable component parts, e.g., plasma and RBCs, are known (within sufficiently controllable ranges), then the respective heights, h2 and h3 may be chosen to appropriately set the location of the interface of separated components therebetween. This interface will thus remain where desired, preferably in the separation channel notwithstanding a substantially continuous inflow of composite fluid to be separated and a substantially continuous outflow of separated components. Note, although a radial direction is preferred for the measurement of these xe2x80x9cheightsxe2x80x9d from a reference circle inward toward the central axis; however, the channels (inlet and outlet) need not be disposed on a radial path. Non-radial and circuitous channel paths may also be effective and provide the pressure drive and balance relationships described herein. Also, the reference line or circle from which the xe2x80x9cheightsxe2x80x9d may be measured may be arbitrary but is preferably within the fluid pathway and here is described relative to the heavier phase separated component (e.g., RBC) outlet from the peripheral channel.
Other similarly derived relationships of interest particularly relative to the dynamic forcing of the fluid flow in this invention, inter alia, are also involved in the systems of the present invention. For example, a further preferred aspect of the present invention involves a preferred relationship between the outlet fluid pressure term(s) and the inlet pressure term, particularly as these are impacted by the selection of the outlet channel heights or lengths h2 and h3 as described above as well as the inlet channel height or length h1. Here, the fluid will flow in a continuous forward fashion so long as the inlet fluid pressure term xcfx811g1h1 is at least greater than either of the outlet fluid pressure terms xcfx812g2h2 and xcfx813g3h3. In an equation form, this relationship is;
xcfx811g1h1 greater than xcfx812g2h2 or, xcfx811g1h1 greater than xcfx813g3h3.
This relationship governs a general forcing of the fluid flow in one direction out of the initial receiving/containment area, into the separation channel and from there into the respective component collection areas.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended merely to provide limited explanation of preferred embodiments of the invention as more broadly claimed. These and further aspects of the present invention will become clearer from the detailed description read in concert with the drawings in which like component elements are referenced therein with like component numbers throughout the several views.